PECULIARITIES OF PLAICE FliOM DIFFERENT FISIHISG GROUNDS. 323 



numbers less frequently. In the females from the Brown Piidges there 

 are two maxima for the dorsal rays : one at 70, the other at 76. 

 Whether this indicates a true dimorphism, like that found by Professor 

 Weldon in the shore crabs of Naples with regard to their frontal 

 breadth, I am not prepared to say, the number of individuals being too 

 small. But it is clear that the females of the Brown Eidges have 

 on the whole a slightly greater number of fin-rays than those of the 

 Norfolk coast, and the same is true of the males. As in other cases, 

 the Plymouth specimens seem to resemble those of the Brown Ptidges ; 

 those from beyond the Dogger Bank to resemble those of the Norfolk 

 coast, in this character. The most frequent number of anal rays in the 

 Norfolk coast and Brown Pidges samples is 55, except in the males of 

 the former, where it is 53 or 54. As in the case of the dorsal rays, the 

 figures show a slight superiority in number of anal rays of the southern 

 samples over the northern, although the difference is not in either case 

 very important. 



Spinidation of the Scales, or Ciliation. In the tables of frequencies I 

 have employed almost the same degrees of spinulation as Duncker, 

 but have distinguished two degrees in the spinulation of the head 

 instead of one. The degrees are (1) on the middle rays of the dorsal 

 and ventral fins only ; (2) also on the head in front of the preopercular 

 bone ; (3) also on the operculum ; (4) also on the skin of the body near 

 the edges, in the region over the interspinous bones ; (5) spinulation 

 extended over other areas of the body. In examining the speci- 

 mens I counted and recorded the number of dorsal and anal fin-rays 

 on which spiuulated scales occurred, and in the first set of tables in 

 which the characters of each specimen are given I have added the 

 numbers together, and given for each specimen the total number of 

 spiuulated rays. One object of this was to ascertain whether the 

 spinulation of the scales extended on to additional rays in proportion to 

 the degree in which it extended to other parts of the body. The result 

 is to show that there is no exact proportion between the number of fin- 

 rays which are spinulated and the extension of the character on other 

 parts of the body. The fact is that scales are also present along the 

 middle rays of the dorsal and anal fins in the females and in the young 

 males, although, like the scales on the other parts of the body, in these 

 cases they are not furnished with spines on their outer edges. In 

 a female 307 cm. long from Plymouth I found that there were 

 rudimentary scales on 24 of the dorsal rays and 21 of the 

 ventral. The spinulation develops at about the time when the male 

 becomes mature, and evidently develops very quickly, although it 

 possibly increases with age. I obtained some male specimens of the 

 Norfolk coast plaice from 20 cm. to 25 cm. in length on purpose to 



